Recombinant DNA technology has provided substantial improvements in the safety, quality, efficacy and cost of pharmaceutical and veterinary medicaments including vaccines. Plant produced mucosal vaccines were invented by Curtiss & Cardineau. See U.S. Pat. Nos. 5,654,184; 5,679,880 and 5,686,079 herein incorporated by reference. Others have described transgenic plants expressing immunoprotective antigens and methods for production including Arntzen, Mason and Lam. See U.S. Pat. Nos. 5,484,717; 5,914,123; 6,034,298; 6,136,320; 6,194,560; and 6,395,964 herein incorporated by reference in their entireties.
Plant cell production using cell culture in defined media avoids the need for animal-sourced components in growth media essentially eliminating the risk of transmitting pathogenic contaminants from the production process. Plants cells are capable of posttranslational glycosylation, and plant cell growth media is generally less expensive, easier to handle and prepare as compared to conventional growth media presently used in the manufacture of vaccines.
Vaccine antigens and proteins of pharmacological or relevant biological activity produced in plant systems offer a number of advantages over conventional production systems. Plant derived subunit proteins cannot revert to virulence (a feature of live conventionally or recombinantly produced live vectored vaccines). Subunit proteins produced from conventional manufacturing methods may be difficult to produce and purify due to protein instability and biochemical extraction issues, and subunit vaccine components that require glycosylation will not be glycosylated when produced in prokaryotes.
Plants provide unique benefits that are difficult to derive from any single conventional or mammalian derived recombinant DNA systems. Traditionally, subunit vaccines or proteinaceous agents are: 1) difficult to purify from recombinant or conventional sources because of low yields making their production prohibitive; 2) unstable due to the proteolysis, pH, or solvents used during purification; 3) less efficacious because they are not native, or the purification process denatures key epitopes; and 4) hampered with extraneous materials of biological origin when produced in mammalian systems (mentioned above).
“Master cell line” principles for biopharmaceutical production utilize live organisms as part of the manufacturing procedure and rely on some basic tenets: 1) a single culture of defined origin and passage history is preserved with defined characteristics of cell phenotype and desired manufacturing features; 2) preservation, typically cryopreservation, is long lasting (spanning several years or more); 3) the cell can be recovered, expanded, passaged indefinitely into “working seed” and subjected to another period of cryopreservation (a principle that requires robustness of the cell; and 4) the cell does not lose the defined characteristics of cell phenotype and desired manufacturing features found prior to the initial cryostate after a defined number of passages.
Thus, the art is in need of plant cells and plant cell cultures that provide for the long term growth, re-cryopreservation, and stability of biomanufacturing target components under master seed principles.